ENGELMANN THE GENUS ISOETES IN N. AMERICA. 363 



1867. In the fifth edition of Gray*s Manual, p. 676, I for the 

 first time published /. echinospora as an American species, dif- 

 fering in several varieties from the European type — var. JSraunii 

 (/. Braunii^ Dur.), var. muricata (/. muricata^ Dur.), and var. 

 Bootti (/. Bootiii^ A. Braun in lit.), all of them from the North- 

 eastern States; also /. Ttickertnanni^ K.V^x^nw in lit., from Mas- 

 sachusetts, and /. saccharqta^ Engelm,, from Maryland. 



1874. In Dr. Parry's Botanical Observations in Western Wyo- 

 ming, Am. Naturalist, viii. 214, 215, T gave an account of the 

 three western species: /. Bolanderi^ Engelm. ; L pygimza^ En- 

 gelm., and /. Niittallii^ A. Br. in lit. 



1877. My notice of /. melanospora^ Engelm,, from Georgia 



was published in the Trans. Acad. Sci. St. Louis, in, 395, note-. 

 1S78. In Coulter's Botan. Gazette for January, p. i, I gave 

 an account of/. Bui/en\'Engelm.^ found in the Indian Territory 

 west of Arkansas. 



§ S. Morphology of Isoetes, 



The species oi Isoetes are the simplest vascular plants known. 

 They consist of a short trunk* witli root- fibres at its base and 

 leaves on its top, normally withoul branching and without any 



axillary productions-f 



The TRUNK is generally depressed, broader than high, or 



flatter in some species (/. Engelmanni)^ and thicker £tnd more 

 globose in others (/- melanopoda)^ but its form is not con- 

 stant; it is concave on the upper side and even somewhat, 

 funnel-shaped where the leaves are Inserted, while the underside 

 shows in almost all the N. American species two grooves and in 

 many exotic ones three grooves, dividing the trunk more or less 

 deeply into two or into three lobes. The number of lobes rarely 

 varies, so that among the many hundreds and even thousands of 

 American specimens which have passed through my hands, I 

 have found only a single, normally bilobed, one with three lobes ; 

 this was an 7. riparia from Philadelphia. In the 3-lobed species 



* A very complete account of the structure nfUie trunk is given by H. Mohl in Linna^a 

 xiv. (iSto) iSi, and of the whole pUml and its morphology by A. Braun in the IsoUes der 

 Insel Sardinien. Monatsbcr. d. Berliner Acad. Wissensch. 1864. 



f Abnormally the /soe/<?5 trunk has been seen divided, probably in consequence of some 

 injury; I myself have seen a specimen of /. Tuchermanl with four distinct bunches of 

 leaves from a single trunk. K. Goebel f »und a proliferous Iso'eies \?ith lateral shoots ia 

 place of spore cases. Bot. Zeitung, 1879, Ho. i. / 



